1. Field of the Invention
The present invention relates to a temperature sensor circuit, mounted on a semiconductor chip, that measures a predetermined temperature and to a calibration method thereof and, more particularly, to a temperature sensor circuit that facilitates high-precision calibration and a calibration method thereof.
2. Description of the Related Art
Temperature sensor circuits constituted by a semiconductor circuit are widely used. For example, in the case of Dynamic Random Access Memory (DRAM), it is necessary to refresh the data of internal memory cells at regular intervals, but the refresh cycle must be changed in accordance with the temperature of the semiconductor chip. That is, when the temperature is low, changes to the data of the memory cell can be slow and the refresh cycle can be extended. However, when the temperature is high, changes to the data of the memory cell are rapid and the refresh cycle must be shortened. Therefore, the temperature sensor circuit is mounted in the DRAM and the refresh cycle is changed in accordance with the sensor output of the temperature sensor circuit.
This temperature sensor circuit generates different temperature-dependent voltages and compares and detects these voltages by means of a differential amplifier circuit to yield an output. Further, as a circuit for generating a temperature-dependent voltage, a bandgap reference circuit may be used, as per Japanese Patent Application Laid Open No. 2002-149252 (published on May 24, 2002), for example.
Furthermore, the differential amplifier circuit of the temperature sensor circuit generally yields an offset. A variety of methods for correcting this offset have been proposed, as per Japanese Patent Application Laid Open No. 2000-165241 (published on Jun. 16, 2000), for example.